Water jacketed,acid containing vessels



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United States Patent 8/1918 Nielsen.

Allen D. Sheakley, Butler, Pennsylvania Aug.6,1968 [45] Patented Nov.10,1970

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[22] Filed n m H O H d n a r 6 S O F n e S S a r t S b M m y e m 0 0 A[73] Assignee Armco Steel Corporation Middletown, Ohio a corporation ofOhio A KE ED ACID CONTAINING VESSELS [54] WATER J C T ABSTRACT: Tanks,pipes and other vessels normally containing acids or other corrosiveliquids are provided with an outer shell which, in cooperation with thevessel it surrounds, forms 6 Claims, 1 Drawing Fig.

a space which is filled with water or other suitable fluid. The fluidwithin the space created by the outer shell, that is, the jacket, ismaintained under a pressure which is greater than that of the liquidwithin the vessel itself. Should a pinhole leak or the like occur in thevessel wall it will immediately be prevented from getting any larger byreason of the fact that the fluid in the jacketed area will flow intothe vessel rather than will the liquid within the vessel continue toflow out.

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-Patented Nov. 10, 1970 'lNVENTOR/S RA LPH Jl/OFFMAN ,1 ALLEN 0SHEA/(LEV %adda, @Zh 1024 ATTOR N EYS 1 WATER JACKETED, ACID CONTAININGVESSELS BACKGROUND OF THE INVENTION 1 Field of the Invention Thisinvention has specific application to pickle tanks such as are used inthe steel industry. These tanks are often part of a continuousmultioperation treatment line and a tank failure would shut down theentire operation. The invention also has direct application to the acidcarrying pipes and other vessels which are in continuous communicationwith the acid contained in the tank.

2. Description of the Prior Art At the outset it should be noted that nosearch has been made either of the patent art or other printedliterature.

Pickle tanks of the type to which this invention has application arefabricated from carbon steel and lined with rubber, plastic or the like. lnside the tank, a layer of brick is placed on the liner to protectit from mechanical damage and to provide thermal insulation. In spite ofthis construction it is not unusual for a leak to develop. In the pastthere was no such thing as a slow leak"; once a pinhole appeared, theacid running down the outside of the tank would cut a destructive groovein the steel in short order. This problem is solved by the instantinvention.

Another problem inherent in prior art tanksof the type briefly describedabove is that of damage due to rapid thermal expansion or contraction ofthe tank shell when the t'ankis drained and refilled with fresh, coldliquid. This problem is also solved by the instantinvention.

Another problem solved by this invention is that of damage to the rubberlining caused by hot spots which develop in specific areas such as, forexample, those adjacent to submerged steam jets or spargers.

SUMMARY OF THE INVENTION The above described problems are solved bysurrounding the tank, pipe or other vessel with a jacket the top ofwhich is sealedand fitted with a few valves to vent air from the jacketwhen it is filled with an appropriate fluid. Pressure is maintained onthe fluid within the jacket so that a static head is established whichexceeds the pressure of the liquid in the tank. By this arrangementleaks will not be a problem because the pressurized fluid within thejacket will flow'jinto the tank through the pinholes as they occur andthus prevent further damage.

In addition to being tolerant of small, pinhole like leaks, the coolingeffect of the water jacket prevents local overheating of therubber linerandthereby minimizes the chances for liner" failure. Such localoverheating is transferred by convection" throughout the mass of thejacketed fluid (normally water).

As above generally indicated, the water volume made possible by thejacket provides a heat reservoir which'will prevent rapid thermalexpansion or contraction of the tank shell proper, even if thetank isdrained and refilled with cold solution or liquid (normally acid).

Neatly capsuled, therefore, the gist of the invention .is to surround anacid containing tank with water under pressure so that should a pinholeappear in the tank, water will immediately flow into the tank throughthis pinhole rather than'will acid flow out of the tank through suchpinhole whereby catastrophic leaking of acid from the tank is prevented.

The objects of the invention are to solve the aforementioned problems inthe manner generally indicated above. A more detailed description of theinvention'follows'.

BRIEF DESCRIPTION OF THE DRAWING The single FIG. disclosing thisinvention comprises what is' largely a cross-sectional vicwof a pickletank to which the invention has been applied, parts being broken awayand other being shown schematically,

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the preferredembodiments, about to be described, of this invention constitute ajacketed pickle tank for use in the steel making industry and ajacketed, acid carrying pipe associated with such tank, it is to beunderstood, and this should be evident to those skilled in this art,that the invention may have broader application than in the specificareas to be described. The description, therefore, although preferred,is also exemplary in nature.

The basic tank construction is conventional; such tank is generallyindicated at 10. The tank shell 11 is fabricated from carbon steel andprovided with a rubber or plastic liner 12. A layer of brick 13 isplaced within the tank on the liner to protect it from mechanical damageand to provide some thermal insulation. Acid or other corrosive liquidis introduced within the tank by means of conventional piping 14 whichmay be plastic lined. Pipe 14 constitutes the supply line which feedsliquid into the tank above the normal level of liquid maintained in thetank. Such liquid is indicated at 15. It should here be noted that thispipe 14 need not have the jacket of this invention applied thereto forthe reason that the acid supply system is intermittently operated andany leaks in this system can be easily repaired or pipe sectionsreplaced while the pickling operation continues.

Thesteel tank shell 11 is supported by a series of Ibeams 16 to which itis fastened. Such beams are illustrated as having flanges 17 and 18, theshell 11 being fastened to the flange 17. All of the side wallsandhorizontal bottom wall are similarly supported. 1 r j The outersteelshell or jacket 19 which constitutes a vital part of this inventionis secured to the flanges 18 of these I- tank shell 11 and jacket shell19. Such closure means 20 may v be provided with a few valves (notshown) to vent air from the jacket when it isfilled. Although airretained in the jacket will not effect'the pressure obtained, it isdesirable to have a sealed, air-free system to minimizecorrosion bylimiting oxygen availability. Pressure within the jacket is maintainedby a stand pipe generally indicated at 2 so that a static head isestablished which exceeds the pressure of the liquid in the tank.Considering the tank liquid 15 to beacid, and the fluid within thejacket 19 to be water, it is necessary to have an elevated standpipebecause acid is more dense than water and the desired pressuredifferential at the bottom of the tank 11 must be maintained. The standpipe 21 is connected directly to the jacket 19 by means of one or morebranch pipes 22. Preferably a plurality of these inputs 22 are providedso that pressure is immediately available to replenish the water supplyat any point in the jacketed system.

It will be apparent that other methods of pressurizing the jacket couldbeutilized. For example, the jacket could be con- ,nected to source ofcompressed airor ordinary water system pressures. It would alsobedesirable to add corrosion inhibitors to the fluid in the jacket if thepressurizing system is such that oxygen is made available to thepressurizing water.

An acid drain line 23 leads from the bottom of the tank shell 11. Thisdrain line or pipe 23 is provided with a liner 24. The pipe 23 issecured by means generally indicated at 25 to the bottom of the tankshell 11 so as to receive acid passing through the passageway 26provided in the brick 13. The drain line 23 is jacketed in a mannersimilar to that applied to the tank 11 and to this end an outer pipe 27is provided was to surround the pipe 23 and create a fluid receivingarea which is in direct communication with the fluid receiving areadefined by the jacket 19. The jacket 27 is secured to the jacket 19 bymeans generally indicated at 28. The stand pipe 21 may be connecteddirectly to the pipe jacket 27. This connection occurs between thepassageway 27 for the tank 11 and the first valve means schematicallyillustrated at 29.

As illustrated, therefore, the drain from the bottom of the tank iswater-jacketed in common with the tank down to the first valve means 29.Since the entire waterjacketing system is a continuous one, asillustrated, it is possible that one stand pipe could provide thenecessary pressure for the entire system. As earlier indicated, however,it is preferred to provide multiple inputs to insure that suitablepressure is available to replenish the water supply at any point in thesystem.

The foregoing describes two of the preferred embodiments of thisinvention, namely, ajacketed tank and ajacketed pipe. It is contemplatedthat the tank and pipe will maintain and carry acid and that the fluidwithin the jackets l9 and 27 will be filled with a supply of water underpressure sufficient that should a pinhole leak occur either in the tankshell 11 or pipe 23 it will immediately be stopped by the flow of thepressurized water thereinto from the jacket system 19, 27. The pinholeleaks are thus prevented from growing and catastrophic leaking isthereby prevented.

With particular regard to pickling operations as carried out in thesteel industry, pickle tanks and pipes provided with the pressurizedwater jacket of this invention will not have to be shut down upon theoccurrence of pinhole leaks. These leaks will be repaired only when theline is down or when the tank is being repaired for some other defect;the leaks per se should never cause a shut down. Thus, as a practicalmatter, leakage of water into the acid bath 15 will cause dilution ofthe acid and, if an excess amount of water leaks into the bath throughthe pinhole leaks aforementioned, this could have an effect on picklingefficiency. In a continuous pickling operation such as this, however,there is always some acid loss due to the acid carried out by the stripas it leaves the acid tank ll and there is some periodic flushing ofspent pickling solution from the tank. Normally such acid loss is madeup by replenishing the tank with additional acid and water as necessary,By the arrangement of this invention, however, part of the waterrequirement for such a replenishing operation would be met by theleakage of water into the bath through the pinholes just mentioned.

If the leakage should take place to such an extent that acid mustfrequently be added, there may be a time at which these leaks should berepaired. By reason of this invention, however, the leakage problem in atank of this type will never cause an emergency type repair but willmerely be dictated by economics. Thus the tank will still be operableeven though it may be necessary to add acid more frequently than isdesirable.

When the tank 11 is emptied, it will almost always be for reasons otherthan the occurrence of pinhole leaks, provided the tank is equipped withthe water jacket of this invention. When the pinhole leaks are to berepaired, the patching technique is the same as has been used before.The steel tank is patched with a steel welded patch, the rubber layer ispatched with a vulcanized rubber seal, and the brick is replaced.

in addition to the advantages stemming from this invention as set forthabove. it is also possible to circulate the water within the jackets 19,27 to the point where tank shell temperature is controlled at anydesired value to protect organic linings or control exothermic chemicalreaction in the bath. This can very well lead to a thinner brick wall,since the thickness of this is determined by the thermal gradientexpected. This in turn will lead to a distinct savings in cost, asavings which may more than offset the extra cost of the steel shellcomprising the jacket 19. it will be understood that a corrosionresistant material such as stainless steel may be used for the tankwalls although this has not been necessary in most cases.

Although the invention has been described with particular reference toits application to a pickling system as utilized in the steel industry,noting further that the invention has been described as specificallyapplied to an acid containing pickle tank and drain line therefrom, itwill be apparent to those skilled in the art that this invention mayhave wider application. it will also be apparent that modifications maybe made in this invention without departing from the scope and spiritthereof. This invention, therefore, is not to be limited to specificstructures and arrangements except insofar as these are explicitly setforth in the subjoined claims.

We claim:

1. Apparatus for checking the growth of leaks in the walls of vesselscontaining corrosive liquids at the pinhole stage, said apparatuscomprising a shell fixed to and spaced from the vessel so as to comprisea fluid containing jacket, said shell being impervious to relativelynoncorrosive fluid, and a supply of noncorrosive fluid in saidjacket,the level of said noncorrosive fluid within said jacket being at leastas great as the level of corrosive liquid within said vessel, saidnoncorrosive fluid within said jacket being under a pressure head whichexceeds the pressure of the corrosive liquid within the vessel, wherebywhen a pinhole leak occurs in the wall of the vessel as caused by thecorrosive liquid therewithin this pinhole leak will be prevented fromgetting larger by reason of the noncorrosive fluid flowing into thevessel from the jacket through the pinhole leak so as to prevent furtherescape of corrosive liquid from the vessel via the pinhole leak.

2. In a carbon steel pickle tank lined with rubber having a layer ofcarbon brick thereon and the tank containing a quantity of acid, theimprovement which comprises: a steel shell fixed to and spaced from theoutside of said tank so as to constitute a water containing jacket, asupply of water in said jacket, the level of water in said jacket beingat least that of the level of acid within said tank, and means formaintaining pressure on the water greater than the pressure of the acidwithin the tank, whereby should the acid cause a pinhole leak in thesteel tank, water will flow through such leak into the tank so as toprevent escape of acid through said pinhole leak.

3. The improvement of claim 2 wherein the means for maintaining saidpressure comprises a stand pipe connected to said jacket.

4. The apparatus of claim 2 wherein there is a drain through the bottomof the tank and a plastic lined drain pipe connected to said tank so asto receive acid exiting the tank via said drain, and including a furtherimprovement wherein said drain pipe is surrounded by another pipe so asto form a jacket thereabout to contain water, water within said lastmentioned jacket, and means to maintain this last mentioned water at apressure greater than the pressure of the acid within the drain pipe.

5. The apparatus ofclaim 4 further improved by providing a connectionbetween the two jackets so that they are in direct water communicationwith each other, and the means to maintain the pressures comprises astand pipe connected to at least one of the said jackets.

6. The improvement of claim 5 wherein said stand pipe has a plurality ofconnections to said jackets, at least one of said connections being tothe jacket for said tank and at least one ofsaid connections being tothe jacket for said drain pipe.

